I have been following a tutorial on setting up REST APIs in Node, using Express for an app that accesses an existing MariaDB database. My version only needs to read data and I have the DB co-located with the Node application (same host).
My goal for this entry-level example is to just access the data, using static SQL, so I can see it rendered in the web page by the JSON pritifier.
[Next, I want to present the data in a table (EJS?). Later, when I can get that to work, I'll add form controls (React?) to let a user specify start and end date bounds for the SQL query. Finally I'll aim to render the data as a line graph (D3js).]
The tutorial runs the web server successfully (it returns 'OK' on the base URL), but when I go to URL/solarData it tries an async function to getMultiple rows from the DB, it responds:
Bind parameters must not contain undefined. To pass SQL NULL specify JS null TypeError: Bind parameters must not contain undefined. To pass SQL NULL specify JS null
at /SunnyData/solarViz/node_modules/mysql2/lib/connection.js:628:17
at Array.forEach (<anonymous>)
at Connection.execute (/SunnyData/solarViz/node_modules/mysql2/lib/connection.js:620:22)
at /SunnyData/solarViz/node_modules/mysql2/promise.js:120:11
at new Promise (<anonymous>)
at PromiseConnection.execute (/SunnyData/solarViz/node_modules/mysql2/promise.js:117:12)
at Object.query (/SunnyData/solarViz/services/db.js:6:40)
at processTicksAndRejections (internal/process/task_queues.js:95:5)
at async Object.getMultiple (/SunnyData/solarViz/services/solarData.js:7:16)
at async /SunnyData/solarViz/routes/solarData.js:8:14
app.js:61
./app.js
const express = require('express');
const app = express();
const port = process.env.PORT || 3800;
const solarDataRouter = require('./routes/solarData');
app.use(express.json());
app.use(
express.urlencoded({
extended: true,
})
);
app.get('/', (req, res) => {
res.json({'message': 'ok'});
})
app.use('/solarData', solarDataRouter);
/* Error handler middleware */
app.use((err, req, res, next) => {
const statusCode = err.statusCode || 500;
console.error(err.message, err.stack);
res.status(statusCode).json({'message': err.message});
return;
});
app.listen(port, () => {
console.log(`Example app listening at http://localhost:${port}`)
});
./routes/solarData.js
const express = require('express');
const router = express.Router();
const solarData = require('../services/solarData');
/* GET solar data. */
router.get('/', async function(req, res, next) {
try {
res.json(await solarData.getMultiple(req.query.page));
} catch (err) {
console.error(`Error while getting solar data `, err.message);
next(err);
}
});
module.exports = router;
./config.js
const env = process.env;
const config = {
db: {
host: env.SUNNY_HOST,
user: env.SUNNY_USER,
password: env.SUNNY_PW,
database: env.SUNNY_DB,
},
listPerPage: env.LIST_PER_PAGE,
};
module.exports = config;
./services/solarData.js
const db = require('./db');
const helper = require('../helper');
const config = require('../config');
async function getMultiple(page = 1){
const offset = helper.getOffset(page, config.listPerPage);
const rows = await db.query(
`SELECT * FROM DTP LIMIT ?,?`, [offset, config.listPerPage]
);
const data = helper.emptyOrRows(rows);
const meta = {page};
return {
data,
meta
}
}
module.exports.getMultiple = getMultiple;
./services/db.js
const mysql = require('mysql2/promise');
const config = require('../config');
async function query(sql, params) {
const connection = await mysql.createConnection(config.db);
const [results, ] = await connection.execute(sql, params);
return results;
}
module.exports = {
query
}
I've left out the ./helper.js
Everything runs fine until I direct the webpage to /solarData. At that point I get the Debug Console (vscode) mentioned up-front
Searching seems to point at a mysql2 shortcoming/bug but not at a practical solution If you respond, please describe the 'bind' mechanism, as I'm not sure what's going on.
Hope I've put enough info in. Please ask if I need to add anything else.
